pkgconf: fix the build with GCC 14

Building pkgconf with GCC 14 currently fails with:
no option '-Wincompatible-pointer-types-discards-qualifiers'

This relaxes warnings for libpkgconf, pkgconf(1), and bomtool(1) until
the improvements are published upstream (see PR #444).

Co-authored-by:	ngie
Approved by:	ngie
Sponsored by:	The FreeBSD Foundation
Event:		Wiesbaden Hackathon 202604
Differential Revision:	https://reviews.freebsd.org/D56591

lib/libpkgconf/Makefile

@@ -12,9 +12,8 @@ SRCS+=		argvsplit.c fileio.c tuple.c dependency.c queue.c
 SRCS+=		path.c personality.c parser.c
 INCS=		bsdstubs.h iter.h libpkgconf-api.h libpkgconf.h stdinc.h
 
-CFLAGS+=	-Wno-error=cast-align
-CFLAGS+=	-Wno-error=cast-qual
-CFLAGS+=	-Wno-error=incompatible-pointer-types-discards-qualifiers
+WARNS?=		3
+
 CFLAGS+=	-DPERSONALITY_PATH=\"/usr/share/pkgconfig/personality.d:/etc/pkgconfig/personality.d:${LOCALBASE:U}/etc/pkgconfig/personality.d\"
 CFLAGS+=	-DPKG_DEFAULT_PATH=\"${LOCALBASE:U}/libdata/pkgconfig:/usr/libdata/pkgconfig:${LOCALBASE:U}/share/pkgconfig\"
 CFLAGS+=	-DSYSTEM_INCLUDEDIR=\"/usr/include\"

usr.bin/bomtool/Makefile

@@ -8,9 +8,8 @@ LIBADD=		pkgconf
 
 PKGCONFDIR=	${SRCTOP}/contrib/pkgconf
 
-CFLAGS+=	-Wno-error=missing-variable-declarations
-CFLAGS+=	-Wno-error=incompatible-pointer-types-discards-qualifiers
-CFLAGS+=	-Wno-error=cast-qual
+WARNS?=		3
+
 CFLAGS+=	-I${SRCTOP}/lib/libpkgconf -I${PKGCONFDIR} -I${PKGCONFDIR}/cli
 
 .PATH:		${PKGCONFDIR}/cli/bomtool

usr.bin/pkgconf/Makefile

@@ -11,9 +11,8 @@ SYMLINKS=	pkgconf ${BINDIR}/pkg-config
 
 PKGCONFDIR=	${SRCTOP}/contrib/pkgconf
 
-CFLAGS+=	-Wno-error=missing-variable-declarations
-CFLAGS+=	-Wno-error=incompatible-pointer-types-discards-qualifiers
-CFLAGS+=	-Wno-error=cast-qual
+WARNS?=		3
+
 CFLAGS+=	-DSYSTEM_INCLUDEDIR=\"/usr/include\" -DSYSTEM_LIBDIR=\"/usr/lib\"
 CFLAGS+=	-I${SRCTOP}/lib/libpkgconf -I${PKGCONFDIR}